Conventionally, an air conditioning unit for a vehicle that includes: a casing that has a partitioning plate for partitioning an upper air passage and a lower air passage; an evaporator that is arranged across the upper air passage and the lower air passage; and a heater unit that is arranged across the upper air passage and the lower air passage and heats cool air blown from the evaporator has been available (for example, see Patent Literature 1 and Patent Literature 2).
In the casing, the partitioning plate on a downstream side in an air flow direction of the heater unit is provided with an opening that communicates between the upper air passage and the lower air passage and a switching door for opening or closing the opening.
Thus, in a foot mode, conditioned air is blown from a foot opening and a face opening in a state that the opening is closed by the switching door. In a bi-level mode, the conditioned air is blown from the foot opening and the face opening in a state that the opening is opened by the switching door. That is, in the bi-level mode, in order to increase a temperature difference between a temperature of the air blown from the foot opening and a temperature of the air blown from the face opening in comparison with that in the foot mode, warm air flows from the upper air passage to the lower air passage through the opening.